1. Field of the Invention
The present invention relates to a method and a device for transmitting signals in a wireless communication system, as well as to a receiving device for receiving signals in a wireless communication system with a special frame structure enabling a high data rate transmission and reception with at least one steerable narrow beam (sharp beam) antenna.
2. Discussion of the Background
Wireless communication is used in a large variety of technical fields, such as mobile telephone, wireless LAN, walky-talkies, broadcast radio systems, point-to-point radio systems and many other known and future applications. The communication radius covered by a respective wireless communication system basically depends on the technique used. Whereas cellular communication systems, such as the GSM and the UMTS system, are adapted for a communication radius up to about 10 km (or more), wireless LAN is in the range of about 100 m (or more) and the Bluetooth system is in the range of several 10 m (or more). The major influences on the communication range of a wireless communication system are the radio frequency and output power used. Although only little absorption of electromagnetic waves in the atmosphere occurs at the radio frequency used for GSM and UMTS, a significant absorption occurs in the 60 GHz range, which makes it quite well suited for low range and indoor wireless communication. Furthermore, the kind of transmission and/or reception antennas used for a respective wireless communication technique varies depending on a respective field of application. For example, if a number of receivers has to be reached or if the location of the receivers is unknown or varies frequently, e.g. due to movement, wide beam antennas or omni-directional antennas are sometimes used. However, the utilization of wide beam antennas in high data rate millimeter wave wireless communication systems is problematic, because of the multi-path fading effect. For example, if wide beam antennas are used both on the transmitter and the receiver side and if the direct line of sight (LOS) link is blocked by an obstacle, such as a moving human being, a vehicle or the like, there exist a lot of reflection paths between the transmitter and the receiver, i.e. transmission paths in which the transmitted electromagnetic wave is reflected at least once by objects before it reaches the receiver. The channel delay spread might be over tens of symbol periods when the data rate is high, e.g. over 1 Gbps, which leads to severe inter-symbol interference due to deep frequency selective fading.
Two conventional solutions exist for such kind of non line of sight (NLOS) user scenarios, whereby both of these solutions need high-speed and complex signal processing circuits. One solution adopts a channel equalizer including linear, decision feedback or maximum likelihood sequence estimation (MLSE) equalizer. When the channel delay spread is much longer than the symbol duration, the equalizer becomes complex and needs a lot of processing power. Another solution is the orthogonal frequency division multiplexing (OFDM) technique, which is already adopted in wireless LAN systems. However, due to its inherent linear modulation and high peak to average ratio problems, the power consumption of the power amplifier (PA) in such systems is very high. Obviously, a high speed Fast Fourier Transformation and other signal processing modules are required for demodulating a 1 Gbps signal. Therefore, it is important to find other solutions which do not require complex and high speed base band circuitry for high data rate millimeter wave range communication systems.